1. Field of the Invention
This invention relates to systems for testing the electrical characteristics of a voice coil member and in particular to a system in which the position of the voice coil member to be tested relative to the tester is not critical to the accuracy of the tests for several different electrical characteristics.
2. DESCRIPTION OF THE PRIOR ART
Disk drives are used extensively for storing information in computer systems. The disks are continuously rotated relative to one or more magnetic transducers which are movable along a substantially radial path relative to the disk by an electromagnetic actuator.
Typically, the transducers are spaced from the disk surface by an air bearing support member which flies at a very small distance above the surface. The transducers are moved to a selected track in response to an address signal supplied to the transducer positioning system which controls the operation of the electromagnetic actuator. The electromagnetic actuator includes the "voice coil", which is positioned adjacent to a magnetic structure so that when the coil is energized, the coil has a tendency to move due to the interaction of the magnetic field from the magnetic structure and the current in the coil.
Transducer positioning systems initially employed an actuator in which a cylindrical type "voice coil" was positioned in the air gap of a cylindrical magnetic pole structure. In this arrangement, the movement was a straight line path. Subsequently because of the desire to minimize the overall size of disk drives, rotary actuators were developed in which a flat coil was employed in place of the cylindrical coil member. By mounting the flat coil on a support member that was affixed to a shaft carrying the head arm assemblies, the coil could be positioned relative to a permanent magnetic structure to cause the shaft to pivot when the coil was energized, thereby moving the transducers along a slightly radial arc relative to the concentric recording tracks.
The electrical characteristics of voice coils become more critical as the track density of the magnetic storage disks increases. As the various technologies involved with disk drives have progressed, the various elements of the head stack assembly of the disk drive have become smaller and smaller. This has led to a serious problem in the manufacture of these assemblies in that the smaller components are more fragile and subject to damage as various steps in the manufacturing process are encountered.
The prior art has generally conducted several tests on the voice coil of the actuator. These tests included a test for the resistance of the coil to ensure it was within predetermined limits. A polarity check is also generally conducted to ensure that the ends of the coil have been connected to the correct terminals. Another test involved checking to ensure that the coil circuit was complete and not open. A similar check was made to ensure that some part of the coil was not shorted out to ground. In the past, the various tests were performed serially, and generally involved moving the entire assembly containing the coil to a series of different test stations. In the past when the various components were not so fragile, there was only a minimal possibility of damage to the various components. However, with current technology, the possibility of damage to the fragile components has increased to the point where the manufacturing process philosophy is to minimize the movement of the head stack assembly and voice coil during the manufacturing process. The present invention provides an electrical test system in which a plurality of required tests are conducted substantially simultaneously on the flat voice coil of a rotary actuator without moving the assembly between tests and with only a minimal concern of the initial position of the coil relative to the test system.